1. Field of the Invention
The present invention relates to an image forming apparatus for detecting the approach of a person, using a sensor, thereby controlling a power state, and a method for controlling the image forming apparatus.
2. Description of the Related Art
There is a growing concern about the environment, and many devices have environment-friendly functions, power saving modes and power usage displays. Image forming apparatuses also have power saving modes and are controlled to shift to those power saving modes when the image forming apparatuses are not in use. For example, a technique for detecting the approach of a person, using a sensor, thereby controlling the image forming apparatus is discussed.
Japanese Patent Application Laid-Open No. 7-288875 discusses a technique for acquiring information from an infrared array sensor for detecting a person, and then determining the presence or absence of a person.
In the technique of Japanese Patent Application Laid-Open No. 7-288875, however, a control function for determining the presence or absence of a person based on the detection result of the infrared array sensor reads information from all the elements of the infrared array sensor to make the determination. This increases the power consumption in the control function. Thus, to further save power, it is necessary to reduce the power consumption in the control function.
With reference to FIG. 17, this technique will be specifically described below.
FIG. 17 is a diagram illustrating the operation modes of a processor for reading data from the infrared array sensor in the conventional art and making a determination.
For example, a description will be given using as an example a case where a processor repeats a normal operation mode 14001, in which the processor reads data from the infrared array sensor and makes a determination, and a low power consumption mode 14002, in which the power consumption is reduced without performing processing.
In the example illustrated in FIG. 17, the time in which the processor operates in the normal operation mode 14001 and which includes the time of access to the infrared array sensor and the calculation time for the determination accounts for about 70% of one cycle. This results in a situation where the processor cannot obtain much of the effect of the low power consumption mode 14002. Although depending on the type of the processor, the power consumption of the processor in this state is about 14.8 mW.
Thus, there is a possibility that reduction of the power consumed in the operation for detecting the approach of a user using a sensor (a human detection operation) can further reduce the power consumption of an image forming apparatus for detecting the approach of a user, using a sensor, thereby shifting a power mode.